Paving The Way For Ship Designs With High Efficiency: MAN Diesel & Turbo’s new G-type engine is designed with a longer stroke to reduce engine speed
by bo svensson
The first MAN Diesel & Turbo Gtype engine, designated G80ME-C, has a design that follows the principles of the large-bore Mk-9 engine series introduced in 2006. The new G-type is designed with a longer stroke to reduce engine speed, thereby paving the way for ship designs with unprecedented high efficiency. MAN Diesel & Turbo said design work for the first G-type is already in progress and final drawings for the structure, moving parts and fuel equipment are scheduled to be ready for delivery in mid-2011.
The delivery of piping and gallery drawings is scheduled to follow in the second half of 2011, assuming final order confirmation has been received by the end of 2010. “MAN Diesel & Turbo always follows developments in the shipping market closely and we have kept a close eye on the trend for fuel optimization in recent years. As such, we have experienced great interest in the G-type engine during extensive consultation with industry partners and are currently working on a variety of projects with shipyards and major shipping lines,” said Ole Grøne, senior vice president, low-speed sales and promotions, MAN Diesel & Turbo. “As a result, we have reached the conclusion that the introduction of the G-type engine program is both viable and timely.”
Tankers and bulk carriers have traditionally used MAN B&W S-type engines with their long stroke and low engine speed as prime movers, while larger container vessels have tended to use the shorter-stroke K-type with its higher engine speed. Larger container vessels, in recent years, have also been specified with S80ME-C9 and S90ME-C8 engines because of the opportunity they offer to employ larger propeller diameters.
“The G-type is an ultra-long-stroke engine and represents the biggest development within our engine portfolio since the successful introduction of the ME electronic engine within the last decade,” said Grøne. “Following efficiency optimization trends in the market, MAN Diesel & Turbo has also evaluated the possibility of using even larger propellers and thereby engines with even lower speeds for the propulsion of tankers and bulk carriers.”
Such vessels may be compatible with propellers with larger diameters than current designs and facilitate higher efficiencies following adaptation of the aft-hull design to accommodate a larger propeller. The company estimated that such new designs offer potential fuel-consumption savings of some 4 to 7% and a similar reduction in CO2 emissions. Simultaneously, the engine itself can achieve a high thermal efficiency using the latest engine process parameters and design features; however, the largest part of the savings comes from the improved propeller performance.
A strict comparison between the S80ME-C9 and the G80ME-C9 shows the stroke of the G-type engine increased from 3450 to 3720 mm, while the mean piston speed dropped from 8.97 to 8.43 m/s, and as a consequence of this, the engine shaft speed dropped from 78 to 68 r/min. The specific fuel oil consumption of the new engine is 167 g/kWh, which is practically the same as for the S80ME-C9 engine. The length of a seven-cylinder S80 engine is 12.03 m, the length of the G80 engine is 12.5 m and the dry mass has increased from 910 to 960 tons. Yet the 7G80ME-C is lighter than the popular 6S90ME-C, often used in VLCCs. MAN Diesel & Turbo also confirms that other G-type engines of different cylinder diameter will be introduced